Yingtai: Do you know much about the validation and frequency of autoclave sterilization effectiveness?
What indicators should be evaluated or monitored for the sterilization effectiveness of pressure steam sterilizers (autoclaves), the monitoring frequency, and the specific methods? The promulgation of the national standard GB/T 30690-2014, *"Monitoring Methods and Evaluation Requirements for Sterilization Effectiveness of Small Pressure Steam Sterilizers,"* has improved the disinfection and hygiene standard system, resolving issues such as the monitoring methods and evaluation requirements for small pressure steam sterilizers.
Distinguishing Between Large and Small Pressure Steam Sterilizers
- Small pressure steam sterilizer: Refers to a pressure steam sterilizer with a volume not exceeding 60 liters.
- Large pressure steam sterilizer: Refers to a pressure steam sterilizer with a volume exceeding 60 liters.
Specific Monitoring Requirements
Pressure steam sterilizers should be tested before initial use after installation, after replacing high-efficiency filters or internal component repairs, and during annual maintenance inspections. The testing items should at least include:
- Sterilization effectiveness testing
- B-D testing (usually not required for small pressure steam sterilizers)
- Pressure gauge and safety valve verification
- Calibration of temperature and pressure sensors (if necessary)
Biological Validation (Biological Indicator Monitoring)
Biological validation involves evaluating sterilization effectiveness using biological indicator spores (Geobacillus stearothermophilus ATCC 7953 or SSIK31).
Procedure (recommended monthly or bi-monthly):
1. During the first sterilization batch, place one biological indicator in the central location (the most challenging area for sterilization inside the sterilizer).
2. After sterilizing at 121°C for 20 minutes, remove the biological indicator and crush the glass ampoule inside.
3. Incubate at 56°C ± 2°C for 48 hours and observe the results.
- Positive (failed sterilization): The culture medium turns from purple to yellow, indicating G. stearothermophilus growth.
- Negative (successful sterilization): No color change, indicating no bacterial growth.
Chemical Indicators (CI)
- Chemical indicator strips: Place the strip in the center of the sterilized items. After sterilization, check for color change. If the color meets the standard, the sterilization is valid; otherwise, the batch must be re-sterilized and retested.
- **3M indicator tape:** Attach the tape to items before sterilization. After sterilization, check for color change. If the color meets the standard, the sterilization is valid; otherwise, the batch must be re-sterilized.
Physical Monitoring Methods
Physical monitoring involves measuring and recording key parameters (e.g., temperature, pressure, time) during sterilization to ensure they remain within the specified range. For example, in steam sterilization, each cycle should continuously monitor and record temperature, pressure, and time to confirm compliance with sterilization requirements. While simple, this method cannot assess external factors like heat distribution or object shape on sterilization effectiveness.
Self-Made Temperature Measurement Tube Method
This method uses chemicals that melt upon heating and solidify into different crystal forms upon cooling. The chemical (e.g., benzoic acid, melting point 121–123°C) is sealed in a small glass tube and placed in the sterilizer. After sterilization, the crystal form indicates whether the required temperature was reached. However, this method cannot verify whether the sterilization duration was sufficient.
Maximum Thermometer Method
This method uses a non-resetting mercury thermometer (similar to a traditional medical thermometer) to measure the highest temperature reached during sterilization. The thermometer is placed in a flask of water in the upper and lower parts of the sterilizer. After sterilization, the temperature is checked against the required standard. Like the tube method, it only verifies temperature, not duration, making it a minimal validation standard.
Maintenance Requirements and Frequency
Pre- and Post-Use Maintenance
- Operated by trained personnel, with the entire sterilization process supervised.
- Wait for steam to discharge and close the exhaust valve before leaving.
- Before sterilization, check for clogged steam inlets and ensure proper water levels in the sterilization chamber.
Routine Maintenance
- Regularly clean the sterilizer's exterior and interior to maintain cleanliness and dryness.
- Periodically clean probes and water level gauges.
Calibration Requirements and Frequency
- Testing frequency:
1. Once per year.
2. After installation, before initial use.
3. After internal component repairs.
- Testing items:
- Sterilization effectiveness (chemical indicator strips, every run).
- Biological effectiveness (biological indicators, at least every 3 months).
- B-D testing (at least every 3 months, except for models with pre-vacuum auto programs that proceed to sterilization only after self-check).
- Pressure gauge verification (every 6 months).
- Safety valve verification (once per year).
